CentOS - Jan 2010 - md boot device

The secondary disc was used in a lab rig to boot off of and test something
after which the primary was replaced and the system was booted off of. It
saw the secondary as more recent and dropped the primary so, the secondary was
removed and the primary was used to boot.

Figuring that made it more recent, even after it was restarted with the
"now
older" secondary, it still wants to drop the primary?

W/o blowing out the secondary (it can't be hot added) how can I force the
primary to not be dropped? I'm amused that even with it used to boot solo,
and hence timestamps validating it as most recent, md will only use the
secondary to start from?

Thanks!
jlc

Joseph L. Casale wrote:
> The secondary disc was used in a lab rig to boot off of and test something
> after which the primary was replaced and the system was booted off of. It
> saw the secondary as more recent and dropped the primary so, the secondary
was
> removed and the primary was used to boot.
> 
> Figuring that made it more recent, even after it was restarted with the
"now
> older" secondary, it still wants to drop the primary?
> 
> W/o blowing out the secondary (it can't be hot added) how can I force
the
> primary to not be dropped? I'm amused that even with it used to boot
solo,
> and hence timestamps validating it as most recent, md will only use the
> secondary to start from?
Unless there is something on the primary that you need to keep, just re-sync 
from the active partition and next time they will come up paired:
mdadm --add md_device missing_partition
cat /proc/mdstat to see the status

If you need to keep something on the primary, remove the secondary and reboot 
several times.  I think there is a count of clean shutdowns that is used to 
determine if one is more current than the other - maybe there is a more 
intelligent way to update it, though.  Then when you get the right one active, 
sync to the other.

-- 
   Les Mikesell
    lesmikesell at gmail.com